For the purposes of Muraganda Petroglyphs, I used to believe that pretty much anything written in a creature's text box that wasn't flavour text was "an ability." The revelation that "CARDNAME is indestructible" was NOT an ability before indestructible was a keyword, and the accompanying statement that "CARDNAME can't be blocked" is STILL not an ability, left me very, very confused. How do you tell what is and isn't an ability? If Phantom Warrior "loses all abilities," is it STILL unblockable??
Those are all abilities. Your “anything other than flavor text” paradigm is a good one.